This invention relates to a friction hinge mechanism used for mounting the displays on laptop computers and other devices. It has significant advantages over hinges of the prior art which can provide only one level of torque. Having a single level of torque poses a problem for present day laptops which have larger and heavier displays but lighter bases, both of which are enabled by recent advances in technology.
The need for different levels of torque can be understood from the following. Low torque is desirable as the laptop is opened so that the base does not have to be held down by the user as the lid is raised. Yet, when the screen is in range of positions for operation of the laptop, higher torque is needed to keep the screen from moving, even when subject to bouncing, as on a train or in a car.
During closing, low torque is permissible, even desirable for ease of motion, until the lid is nearly closed. But then a higher torque is needed to prevent the lid from slamming shut which may cause damage to the fragile elements in the display.
The hinge of our invention can also provide torque to cause the lid to pop-up, an additional feature much sought after by laptop customers, and therefore, by the designers and manufacturers of these devices. Those who supply friction hinges to the laptop industry are often asked for pop-up hinges. That is, hinges that will cause the display to open slightly when the latch is released so that the user can more easily open the computer. Those laptops without this feature often require that the lid be lifted by the user. Releasing a single latch in the center while raising the lid can be awkward. Providing a latch on each side, where the hands must be positioned to raise the lid, increases cost, weight, and complexity. The pop-up feature of our hinge derives from the same components that provide the two-level torque. So no additional components or expense are required to achieve this benefit.
There are several techniques employed for producing friction in hinges. The hinge of our invention uses question-mark shaped bands wrapped tightly about a round shaft. Those familiar with the art of such friction hinges will be aware that the torque produced by such bands is lower for one direction of rotation about the shaft, and higher for the other. The torque required to produce rotation in the direction that tends to unwrap the band is lower. For a hinge made with two bands, one connected to each of the two elements being rotatably hinged, and wrapped in the same direction about a common shaft, the torque needed to rotate one band relative to the other will be the lower value for either direction of rotation. This occurs because one of the bands will tend to unwrap for one direction of rotation, while the other band will do so for the second direction of rotation. This arrangement of bands is used in our invention to provide the lower sought-after torque through most of the opening and closing motion of a laptop computer.
However, it is still necessary to provide a higher torque for holding the lid at the two ends of its range of motion: in the open position for viewing, and near the closed position to prevent slamming shut. This is accomplished by adding features to the shaft and bands to limit their relative motions at these positions. So, the band that tends to unwrap as the lid is opened reaches a stop when the lid nears the angle for viewing. Since that band can no longer slip about the shaft, further motion of the lid will force the other band to slip about the shaft. Since this other band tends to wrap down, or tighten about the shaft for that direction of rotation, a higher torque is required to cause slippage. This higher torque holds the lid in position during use.
Similarly, during closing, the other band slips more easily until it reaches its stop on the shaft. Thereafter, further rotation of the lid causes the one band to slip at its higher torque. This prevents the lid from closing too fast.
A device incorporating this type of hinge and a latch to keep it fully closed will exhibit some tendency to pop open when the latch is released because the higher torque at closing will produce some distortion in the tails of the band elements and in the plastic materials of which the cases of such devices are usually made. An optional feature that can be added to the hinge of our invention increases the pop-open action. This is achieved by so arranging the stop features that just before reaching the fully closed position, neither band can rotate further in that direction. Then a still larger torque is required to fully close the lid and engage the latch. Upon opening, the energy stored in the spring material of the bands and the deflection of the case materials is released, lifting the lid a few degrees.
Our hinge has one or more band elements that are firmly connected to the lid of the device to be hinged, and one or more band elements firmly connected to the base of the device. A shaft passes axially through all of the band elements, providing the connection between the lid and the base. In the simplest embodiment, when the assembled device is viewed from an end of the shaft, the band elements are wrapped in the same direction about the shaft. The shaft has stop features which interact with corresponding features on at least some of the bands to limit motion between band and shaft.
For the simplest embodiment having two band and a shaft, the stop feature limits the angle of rotation of each band relative to the shaft, and the total angle through which the hinge can operate is the sum of these two angles plus any slight amount beyond that sum used for the pop-up feature. It is not necessary for the two bands to have equal angles of operation. This flexibility can be used to achieve advantages in design.
It is an object of our invention to provide friction hinges for laptop computers and for other electronic displays and devices whose operation can benefit from differing torque levels during different portions of their relative movement.
It is a further object of our invention to furnish a friction hinge system for laptop computer displays that allows them to move easily from the closed condition toward the operating range of positions and then provides a greater torque for maintaining the angular orientation during operation, while still permitting accurate adjustment.
It is still a further object of our invention to provide friction hinges for electronic displays that are easily moved and yet prevent the display from banging against its latch.
It is also an object of our invention to provide friction hinges for electronic displays that spring open upon release of a latch.
The inventive pop-up friction hinge system accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the constructions described hereinafter, and the scope of the invention will be indicated in the claims.